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Assessment of Antibiotic Resistant Commensal Bacteria in Food

Lehman, Mark
http://rave.ohiolink.edu/etdc/view?acc_num=osu1392303234

Abstract Details

2006, Master of Science, Ohio State University, Food Science and Technology.
The rapid emergence of antibiotic resistant (ART) pathogens is a major public health concern. Although antibiotic resistance (AR) in foodborne pathogens has been studied extensively, the contribution of foodborne commensals in disseminating the resistance genes has been neglected in the past. Foodborne pathogens only account for a very small portion of microbes associated with food; meanwhile, AR encoding genes can be transferred readily from commensals to pathogens by natural gene transfer mechanisms. Horizontal transmission of genetic material from one organism to another has been established as a major mechanism for the expedited development of resistance. The impacts of antibiotic applications in clinical treatments, veterinary medicine, animal husbandry practices and animal feed on the emergence of antibiotic resistance (AR) have been well-documented. However, knowledge on other major routes in the dissemination of AR is limited. This information is essential to properly evaluate the contribution of food chain in the evolvement of AR pathogen, particularly in susceptible host populations. The objective of this study is to reveal the significance of the food chain in AR dissemination by investigating the prevalence of ART commensal organisms in a variety of ready-to-eat (RTE) and raw foods, Samples were evaluated for the total microbial counts, as well as resistant population for tetracycline (Tet) and erythromycin (Em). All food items were analyzed within the use-by dates. RTE salad mixes contained ART population greater than 103 CFU/g, more than 80% of which were resistant to erythromycin. Block cheeses had resistant counts greater than 102 CFU/g. Raw meat products, both raw and cooked shrimps all have resistant population greater than 102 CFU/g. Further studies confirmed the presence of mobile AR genes in the food isolates, by assessing the presence of AR genes in ART commensals and their transmission to human residential bacteria, using ermC gene as an example. Nine RTE bagged salads and nine RTE deli-meats from local retail stores were examined for the prevalence of tetracycline-resistant (Tetr) and erythromycin-resistant (Emr) bacteria using plate count agar (PCA) with tetracycline (16µg-mL-1) or erythromycin (50µg-mL-1), and without antibiotics. Cycloheximide (100µg-mL-1) was added to all plates to inhibit the growth of molds and yeasts. All nine salad samples contained at least 103 CFU of Emr bacteria per gram of food., but the ART bacteria were only found in RTE deli meats sporadically. A total of 108 Emr colonies were screened by conventional PCR and nearly 14% possessed the ermC gene. The ermC isolates were found to be either Pseudomonas spp. or Staphylococcus spp. using partial 16S rRNA gene sequence analysis . The ermC gene from a salad Staphylococcus epidermidis isolate was transferred to Streptococcus mutans UA159 by natural transformation. The ermC gene was found associated with a plasmid(s) of approximately 2.4 kb to 4.0 kb in both the S. mutans transformants and the Staphylococcus epidermidis donor strain by Southern blot analysis. The minimum inhibitory concentration (MIC) of Em for the transformants was significantly increased compared to the parental S. mutans strain, but comparable to the donor strain. These data suggest that ART bacteria are prevalent in the food chain and might serve as a potentially important avenue transmitting AR genes to human microflora and possibly pathogens.
Hua Wang (Advisor)
Ahmed Yousef (Committee Member)
Randall Harris (Committee Member)
106 p.
Food Science

Recommended Citations

Citations

  • Lehman, M. (2006). Assessment of Antibiotic Resistant Commensal Bacteria in Food [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1392303234

    APA Style (7th edition)

  • Lehman, Mark. Assessment of Antibiotic Resistant Commensal Bacteria in Food. 2006. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1392303234.

    MLA Style (8th edition)

  • Lehman, Mark. "Assessment of Antibiotic Resistant Commensal Bacteria in Food." Master's thesis, Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1392303234

    Chicago Manual of Style (17th edition)

osu1392303234
242
© 2006, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.